airboat with 3w70
06-09-2013, 12:00 PM
#2
Senior Member
Join Date: Nov 2004
Location: onalaska,
WI
Posts: 1,791
Likes: 0
Received 0 Likes
on
0 Posts
RE: airboat with 3w70
[X(]
Well...since the engine will never really unload like it would if it were on a plane, you could run a 22" 3 blade prop to keep the CG down low. The boat will need to be just a tad wider than the diameter of the prop....say, 26- 30 wide and 39 - 53 long using 175% length to width ratio, You can adjust the ratio depending on how you want it to act in the water. A wider/ shorter boat will slide easier than a banking corner narrow/long boat. Mock it up in cardboard first to see if it's how you want it to look.
That will be a BIG boat if you decide to build it.
Well...since the engine will never really unload like it would if it were on a plane, you could run a 22" 3 blade prop to keep the CG down low. The boat will need to be just a tad wider than the diameter of the prop....say, 26- 30 wide and 39 - 53 long using 175% length to width ratio, You can adjust the ratio depending on how you want it to act in the water. A wider/ shorter boat will slide easier than a banking corner narrow/long boat. Mock it up in cardboard first to see if it's how you want it to look.
That will be a BIG boat if you decide to build it.
06-09-2013, 12:18 PM
#4
Senior Member
Join Date: Nov 2004
Location: onalaska,
WI
Posts: 1,791
Likes: 0
Received 0 Likes
on
0 Posts
RE: airboat with 3w70
Correct, that and no dive bombs.
The CG (center of gravity) is an imaginary point somewhere above the hull, but below the engine, center line, and ahead of the engine. A smaller prop just keeps it from being tippy, an inverted engine will also lower the CG. The CB (center of balance) is just that, the point at which the boat will balance if placed on a cylindrical object.
The CB is usually around 30% or 1/3 the length of the hull from the transom. A 30 inch hull would have a center of balance of about 10 inches from the stern.
The CG (center of gravity) is an imaginary point somewhere above the hull, but below the engine, center line, and ahead of the engine. A smaller prop just keeps it from being tippy, an inverted engine will also lower the CG. The CB (center of balance) is just that, the point at which the boat will balance if placed on a cylindrical object.
The CB is usually around 30% or 1/3 the length of the hull from the transom. A 30 inch hull would have a center of balance of about 10 inches from the stern.
